Google Drive lets you view these file types:

Image files (.JPEG, .PNG, .GIF, .TIFF, .BMP)
Video files (WebM, .MPEG4, .3GPP, .MOV, .AVI, .MPEGPS, .WMV, .FLV)
Text files (.TXT)
Markup/Code (.CSS, .HTML, .PHP, .C, .CPP, .H, .HPP, .JS)
Microsoft Word (.DOC and .DOCX)
Microsoft Excel (.XLS and .XLSX)
Microsoft PowerPoint (.PPT and .PPTX)

Adobe Portable Document Format (.PDF)
Apple Pages (.PAGES)
Adobe Illustrator (.AI)
Adobe Photoshop (.PSD)
Tagged Image File Format (.TIFF)
Autodesk AutoCad (.DXF)
Scalable Vector Graphics (.SVG)
PostScript (.EPS, .PS)
TrueType (.TTF)
XML Paper Specification (.XPS)
Archive file types (.ZIP and .RAR)